An error occurred while compiling the firewall on books.

An error occurred while compiling the firewall in the book-Linux general technology-Linux programming and kernel information. The following is a detailed description. // User_firewall.c
# Ifndef _ KERNEL __
# Define _ KERNEL __
# Endif
# Ifndef MODULE
# Define MODULE
# Endif
# Include
# Include
# Include
# Include
# Include
# Include
# Include
# Include
Static unsigned int user_firewall (unsigned int hooknum, struct sk_buff ** skb, const struct net_device * in,
Const struct net_device * out, int (* okfn) (struct sk_buff *))
{
Struct iphdr * iph;
Struct tcphdr * tcph;
Struct udphdr * udph;

_ U32 sip;
_ U32 dip;
_ 2010sport;
_ B2dport;

Iph = (* skb)-> nh. iph;
Sip = iph-> saddr;
Dip = iph-> daddr;

If (iph-> ihl! = 5)
{// Check the checksum
Printk ("IP packet with packet from % d. % d. % d. % d to % d. % d. % d. % d \ n ", NIPQUAD (sip), NIPQUAD (dip ));
}

If (iph-> protocol = 6)
{Tcp protocol
Tcph = (struct tcphdr *) (_ u32 *) iph + iph-> ihl );
Sport = tcph-> source;
Dport = tcph-> dest;
Printk ("Source port: % d \ n", ntohs (tcph-> source ));
Printk ("Dest port: % d \ n", ntohs (tcph-> dest ));
If (tcph-> syn) & (sport = dport) & (sip = dip ))
{
Printk ("maybe land attack \ n ");
}
If (ntohs (tcph-> dest) = 139 & tcph-> urg)
{
Printk ("maybe winnuke a from % d. % d. % d. % d to % d. % d. % d. % d \ n ", NIPQUAD (sip), NIPQUAD (dip ));
}

}

Else if (iph-> protocol = 17)
{// Udp protocol
Udph = (struct udphdr *) (_ u32 *) iph + iph-> ihl );
Sport = udph-> source;
Dport = udph-> dest;
Printk ("Source port: % d \ n", ntohs (udph-> source ));
Printk ("Dest port: % d \ n", ntohs (udph-> dest ));
//...................................... ..
}

Else
{
Printk ("unknown protocol % d packet from % d. % d. % d. % d to % d. % d. % d. % d \ n ", iph-> protocol, NIPQUAD (sip), NIPQUAD (dip ));
}
Return NF_ACCETR;
}
Static struct nf_hook_ops iplimitfilter =
{
{NULL, NULL },
User_firewall,
PF_INET,
NF_IP_PRE_ROUTING,
NF_IP_PRI_FILTER-1
};
Int init_module (void)
{
Return nf_register_hook (& iplimitfilter );
}
Void cleanup_module (void)
{
Nf_unregister_hook (& iplimitfilter );
}


The book says: gcc-O-c-Wall user_firewall.c
But there are many header file errors. My kernel version is 2.4